This invention relates to shock isolators and, more specifically, to shock isolators that can simultaneously provide compressive support without reliance on a direct axial compressive path through the isolator material.
Various elastomeric materials have been used, or suggested for use, to provide shock and/or vibration damping as stated in U.S. Pat. No. 5,766,720, which issued on Jun. 16, 1998 to Yamagisht, et al. These materials include natural rubbers and synthetic resins such as polyvinyl chlorides, polyurethane, polyamides polystyrenes, copolymerized polyvinyl chlorides, and poloyolefine synthetic rubbers as well as synthetic materials such as urethane, EPDM, styrene-butadiene rubbers, nitrites, isoprene, chloroprenes, propylene, and silicones. The particular type of elastomeric material is not critical but urethane material sold under the trademark Sorbothane(copyright) is currently employed. Suitable material is also sold by Aero E.A.R. Specialty Composites, as Isoloss VL. The registrant of the mark Sorbothane(copyright) for urethane material is the Hamiltion Kent Manufacturing Company (Registration No. 1,208,333), Kent, Ohio 44240.
Generally, the shape and configuration of elastomeric isolators have a significant effect on the shock and vibration attenuation characteristics of the elastomeric isolators. The elastomeric isolators employed in the prior art are commonly formed into geometric 3D shapes, such as spheres, squares, right circular cylinders, cones, rectangles and the like as illustrated in U.S. Pat. No. 5,776,720. These elastomeric isolators are typically attached to a housing to protect equipment within the housing from the effects of shock and vibration.
The prior art elastomeric isolators are generally positioned to rely on an axial compression of the elastomeric material or on tension or shear of the elastomeric material. Generally, if the elastomeric isolator is positioned in the axial compressive mode the ability of the elastomeric isolator to attenuate shock and vibration is limited by the compressive characteristics of the material. On the other hand, in the axial compressive mode the elastomeric isolators can be used to provide static support to a housing, which allows a single elastomeric isolator to be placed beneath the housing to support the static weight of the housing.
In general, if the elastomeric isolators are positioned in the shear or tension mode as opposed to an axial compression mode the elastomeric isolators provide better shock and vibration attenuating characteristics in response to dynamic forces due to shock and vibration. Unfortunately, elastomeric isolators, which operate in a shear or tension mode or in the axial compression mode, can generally not be placed beneath a housing to provide static support to the housing without substantially effecting the shock and vibration attenuation characteristics of the elastomeric isolators. Consequently, to provide static support for a housing, as well as effective shock and vibration attenuation characteristics the elastomeric isolators, which operate in the shear or tension mode, are generally placed along side or above a housing so that the elastomeric isolators can function in a shear or tension mode while tensionally supporting the static weight of the housing. The positioning in a shear or tension mode can require placing matching elastomeric isolators on each side of the housing. In contrast, the present invention provides an elastomeric isolator that provides axial offset compressive support for a housing. As the present invention does not require paring with other elastomeric isolators a single elastomeric isolator can be placed beneath a housing to provide static support for the housing through an axial offset compressive axis while at the same time allowing the elastomeric isolator to retain the necessary dynamic attenuation characteristics to thereby effectively reduce shock and vibration to the housing.
U.S. Pat. No. 4,059,254 shows an energy absorbing unit comprising an elastomeric member arranged in a trapezoidal configuration. A sliding piston is incorporated in the unit which has limited displacement due to a pin that slides within a elongated slot.
A triad shock isolator having a triad of elastomer legs that coact to cantileverly support the weight of a housing though an axial offset compressive axis while at the same time effectively attenuating shock or vibration imparted to the housing or in an alternate embodiment a tetrahedron isolator having a cavity therein with the tetrahedron isolator having an axial offset compressive axis to cantileverly support a housing while at the same time effectively attenuating shock and vibration imparted to the housing.